Research On Context-Aware Computing Technology And Its Application In Semantic Web Services

Pervasive services, whose objective is to build an open and ubiquitous environment to provide users with intelligent and personalized information and services, are the shared vision of computer networking and wireless communications. Integration of context-aware computing and semantic Web services is one of the effective approaches to realize pervasive services. On the basis of context modeling and reasoning, context-aware semantic Web services discovery and delivery are in-depth researched in this dissertation. In sum, the main contributions are as follows:1. Context modeling is the basis and precondition of context-aware computing. Therefore, ontology-based context modeling is first lucubrated in this thesis, and the existing context ontologies are improved by utilizing context lattice and RDF reification to construct a universal context model which can describe the semantic of various types of contexts such as physical context, computing context, social context and task context, etc. Moreover, the description methods of spatiotemporal data, i.e. Allen's Interval Algebra and Regional Connection Calculus, are introduced into context-aware computing so as to enhance capability of the expressions of the spatio-temporal data and lay the foundation for context reasoning, semantic similarity calculating as well as context-ware Web services.2. Rule-based and ontology-based reasoning technologies are utilized to implement spatial and temporal reasoning which apply within the context-aware computing. As temporal reasoning is concerned, duration reasoning and temporal relation reasoning are proposed. While, in respect of spatial reasoning, the problems such as consistency checking and implicit information obtaining are addressed. The performance evaluation results indicate that the presented methods are efficient.3. An annotation-based mechanism for combining context model with service request and description is presented in the thesis. On this basis, context-aware Web service discovery is also proposed, which can be divided into three phases: context matching, interface matching and QoS-based ranking. In addition to general-purpose context matchmaking algorithm which perform in the phase of context matching, special algorithms for matching of the temporal, spatial and device contexts are introduced. Furthermore, prior to interface matching, some candidates which are unrelated to the service request in terms of context, can be filtered through context matching, as a result the frequency of the execution of interface matching is reduced, and the efficiency and precision of service discovery are improved. 4. One of the most important technical problems arise after Web service discovery is how to determine the manner of service delivery. With regards to this, a rule generation method is proposed. Context-aware systems are regarded as decision systems, and context information are reduced with discernibility matrix so as to generate rules. System can automatically select an appropriate form of service delivery. In addition, because data can be utilized is limited, the generated rules can not entirely cover the domains of contexts. The rule matches current context probably does not exist. A rule matching algorithm based on semantic distance is presented as the solution to this problem.